<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body></body>
  <script>
    // 页面加载完成后再执行
    onload = function () {
      var xhr1 = null,
        xhr3 = null,
        xhr4 = null;
      // 使用定时器的目的：避免请求的时间过长
      setTimeout(function () {
        // 实例化请求对象
         xhr1 = new XMLHttpRequest();
        // 创建请求
        xhr1.open(
          "get",
          "https://cdn.bootcdn.net/ajax/libs/jquery/3.3.1/jquery.min.js",
          true
        );
        // 向后台发送请求
        xhr1.send();

         xhr3 = new XMLHttpRequest();
        xhr3.open(
          "get",
          "https://img1.baidu.com/it/u=3750617966,2166234761&fm=253&app=138&size=w931&n=0&f=JPEG&fmt=auto?sec=1692378000&t=92ac7061344549bd062c8083af726dbd",
          true
        );
        xhr3.send();

         xhr4 = new XMLHttpRequest();
        xhr4.open(
          "get",  
          "https://img0.baidu.com/it/u=1644269549,4064438186&fm=253&app=120&size=w931&n=0&f=JPEG&fmt=auto?sec=1692378000&t=f991bdb8a2339039fe222f31df1ef36e",
          true
        );
        xhr4.send();
        
        // 调用数据
        xhr1.onreadystatechange = function () {
        if (xhr1.readyState == 4 && xhr1.status == 200) {
          console.log(xhr1.responseText);
        }
      };
      }, 1000);
    };
  </script>
</html>
